I don't see why
Cirdan would have stayed to the very last
Elf. How could he even know who was surely 'last' (foresight? see below), but moreover, why would he need to, or want to?
Of The Rings Of Power echoes Cirdan's statement to
Gandalf in
The Lord of the Rings appendices.
'... and I will dwell by
the grey shores, guarding the Havens until the last ship sails. Then I will await thee.'
Again 'thee' here is Gandalf, but what about this 'last ship'?
'White was that ship and long was it a-building, and long it awaited the end of which Cirdan had spoken. But when all these things were done, and the heir of
Isildur had taken up the lordship of
Men, and the dominion of the West had passed to him (...) and Master
Elrond took there the ship that Cirdan had made ready.'
This ship is the 'last ship' in my opinion, although some appear to have a problem with
last because it isn't technically the last ship ever. Still, whatever you call it, and for whatever reason (the last ship of major historical note? since it marked the passing of very notable figures leaving
Middle-earth together in an 'end of era' sort of way?),...
... it seems to me that Cirdan is guarding the Havens until
this ship sails, as this is the ship that awaited such things as
Aragorn taking up the throne and so on (see the fuller quote in the book).
But then again (Appendix A):
'(...) At
the Grey Havens dwelt Cirdan
the Shipwright, and some say he dwells there still, until the Last Ship sails into the West. In the days of the
Kings most of the
High Elves that still lingered in Middle-earth dwelt with Cirdan or in the seaward lands of
Lindon. If any now remain they are few.'
I'm not sure of the timing of this statement (the whole passage actually), in other words, who wrote it and when was it written (what time does this 'now' refer to)? I have yet to investigate this one in detail to see if something more might be said here (anyone?). And there is the element of 'some say' too.
But in any event, there is also the element of Cirdan's great desire in the
First Age:
'Nonetheless it is said that for love of his kin and allegiance Cirdan was the leader of those who sought longest for Elwe when he was lost and did not come to the shores to depart from Middle-earth.
Thus he forfeited the fulfilment of his greatest desire: to see the Blessed Realm and find again there Olwe and his own nearest kin.'
JRRT, Cirdan, Last Writings
Cirdan even states:
'I will follow that light [of Eressea], alone if none will come with me, for the ship that I have been building is now almost ready.' But he receives a message from the
Valar to stay, and obeys, and by implication of his seeming vision (described in the text), this was a message to abide because he would be involved in building
Earendil's ship.
Of course, if the argument is that Cirdan would surely want to pass Oversea once Earendil's ship was finished and
Morgoth defeated, why then stay at the end of the First Age?
The late text concerning Cirdan also notes that:
'From that night onwards Cirdan received a foresight touching all matters of importance, beyond the measure of all other Elves upon Middle-earth.' [compare to Appendix B: 'For Cirdan saw further and deeper than any other in Middle-earth, and he welcomed Mithrandir at the Grey Havens, knowing whence he came and whither he would return.']
So it might be argued that he remained because he knew, even if in some vague way, that he had a role to play in Middle-earthian conflicts to come, and especially in the aiding of Gandalf (ultimately surrendering a
Ring of Power to him), and so in the ultimate defeat of
Sauron. And thus one might say that he considered his task completed after this incarnation of
evil (Sauron) was finally overthrown.
There is also the implication (although the timing was not known) that when
Celeborn sailed: with him went the last living memory of the Elder Days. Cirdan could be said to have had living memory of the Elder Days of course, but was he already gone in any case? And couldn't Treebreard, for instance, also be said to have living memory of the Elder Days?
It's hard to raise a compelling argument here, but again I see no great reason for Cirdan to have desired to await some vague 'last ship' -- awaiting (in theory) the passing of some of the
Silvan Elves from
Mirkwood or something. But then, as also noted already, one could argue he maybe had a foresight that told him when the 'last Elf' would leave!
That said, I think there is a certain beauty behind the idea of Cirdan remaining for all Elves who would ever seek the Sea. It's a nice concept in itself, and I think its attractiveness is part of what sways interpretations on this issue. I'm sometimes almost swayed there myself, or like to say that both ideas are 'textually possible' so to speak, even if both are not possible internally (that is, obviously he can't both have sailed with Gandalf and remained for every last Elf seeking the West).
But as of today anyway, I still lean a bit toward: Cirdan sailed with Gandalf :*)