It is possible that the Elder Wand might not choose the wizard who conquers it. If it is always the wand that chooses the wizard, any given wand might also not choose a wizard, even in the instance of a wand being won in a duel. Here, Harry is talking to Mr. Ollivander, the Wandmaker, about Draco Malfoy's want, which Harry took from Draco by force:
‘– then it may be yours. Of course, the manner of taking matters. Much also depends upon the wand itself. In general, however, where a wand has been won, its allegiance will change.’
There was silence in the room, except for the distant rushing of the sea.
‘You talk about wands like they’ve got feelings,’ said Harry, ‘like they can think for themselves.’
‘The wand chooses the wizard,’ said Ollivander. ‘That much has always been clear to those of us who have studied wandlore.’
‘A person can still use a wand that hasn’t chosen them, though?’ asked Harry.
‘Oh yes, if you are any wizard at all you will be able to channel your magic through almost any instrument. The best results, however, must always come where there is the strongest affinity between wizard and wand. These connections are complex. An initial attraction, and then a mutual quest for experience, the wand learning from the wizard, the wizard from the wand.’
The sea gushed forwards and backwards; it was a mournful sound.
‘I took this wand from Draco Malfoy by force,’ said Harry. ‘Can I use it safely?’
‘I think so. Subtle laws govern wand ownership, but the conquered wand will usually bend its will to its new master.’
Deathly Hallows - page 399 - Bloomsbury - chapter 24, The Wandmaker
Mr. Ollivander says that a conquered wand -- which would presumably include the Elder Wand -- will "generally" and "usually" bend its will to the new owner, but he does not say a conquered wand will always do so.
I noted that you said, "wands choose their owners more so than the other way around." According to Ollivander, the wand chooses the wizard. Period. Can a wand's will be bent? Yes. But not always. And although a wizard can still use a wand that hasn't given its allegiance, the best magical results can only occur when the wand and wizard are on a mutual quest (see above).
Yes, the Elder Wand could not choose the new owner.
ETA: Tales of Beedle the Bard was niggling in the back of my mind after I answered this, so I checked The Tale of the Three Brothers and found something interesting about the Elder Wand:
Most witches and wizards prefer a wand that has
“chosen” them to any kind of second-hand wand,
precisely because the latter is likely to have learned
habits from its previous owner that might not be
compatible with the new user’s style of magic. The
general practice of burying (or burning) the wand
with its owner, once he or she has died, also tends
to prevent any individual wand learning from too
Believers in the Elder Wand,
however, hold that because of the way in which it
has always passed allegiance between owners – the
next master overcoming the first, usually by
killing him – the Elder Wand has never been destroyed or buried, but has survived to accumulate
wisdom, strength and power far beyond the
Tales of Beedle the Bard - pages 102 - 103 - Bloomsbury - The Tale of the Three Brothers
- Wandlore tells us that the wand chooses the wizard. It also tells us that it is possible for a conquered wand to not change its allegiance to the wizard that won it.
- Believers in the Elder Wand proport that it has never failed to switch its allegiance when beaten in a duel. However, the rules of wandlore don't preclude the possibility of the Elder Wand failing to change its allegiance. Perhaps it had not done so previously. But that doesn't mean it couldn't choose to withhold its allegiance in the future.
So I'm sticking to my original answer of Yes, the Elder Wand could choose to not give its allegiance to a new owner.