Well, so far, we've only got 60 votes (as I write this), so, it's not exactly a burning question. I usually don't start taking these kinds of polls seriously until we get over 100 votes. And, even then, it's so self selective.
Speaking for me personally, I want to see a warlord over a psion for a couple of reasons.
1. The psions that people have talked about all follow the same vein as earlier editions - a completely new subsystem complete with a new class and multiple subclasses. Similar to Complete Psionics in 2e or the 3e psionics system. For me, that's a hard no. I have zero interest in a class that requires me, as a dm, to read several hundred pages of rules for one player at the table to use. If the psion doesn't fit into existing mechanics and preferably existing classes, the way they've been doing it in the UA's, then I have zero interest. I'll pass on it the same way I did in every other edition.
2. Warlord is THE iconic class from 4e. It sends a very clear message to 4e players and fans that we are welcome in the big tent and that WotC isn't taking sides in the edition war. We're all D&D gamers and it would mean a lot if my preferences were recognized as being equal to anyone else's.
3. There is, in my mind, an open design space for a warlord in the game. We have FIVE classes capable of magical healing. But, no one capable of non-magical healing. There are several support subclasses - cleric, bard, etc - but almost all the support is magical in nature. 5e has doubled down on the magic level of the game to the point where virtually every round of every encounter features multiple spells being cast. Adding a warlord counter balances this by giving us specifically non-spell/non-magic features. A psion, of whatever flavor, is just another caster in a game that has 33 out of 36 base sub-classes already casting spells.