The real question is, is it now 4.5?
I really can't see Wizards doing a reprint of the Player's Handbook, Monster Manual or DMG no matter what they say at this point.
I think we have to say that it's 4.4999999999. Some people will never say it's 4.5 because Scott Rouse said that there would not be one, therefore even if a book came out called "4.5", they would say it doesn't count as 4.5. Some will never say so because you can
technically play the state-of-the-art game without buying new books, as long as you download and print the dozens of pages of errata. Some will never say so because 3.5 meant something to them, positive or negative, that 4.4999999999 does not.
I think of it as 4.5 because basically the rules have been re-done and the classes and the design philosophy have all been updated. In 3.0 to 3.5 there were some serious differences but only serious enough for a rules wonk to notice. To me they're practically the same game. OK, so "Keen" and "Improved Critical" no longer stack... that's basically just an erratum to de-brokenify a stupid combo (vorpal scimitar, anyone?). Pretty much, to me anyway, 3.x is 3.x. It's not all identical (thus the ".x"), but it's all the same enough that I don't really like any of it.
But to some folks, "4.5" seems to take on this vast, dreadful meaning that I don't grok. Like something fundamental in the cosmos would have shifted into the darkness but it hasn't therefore it's not 4.5. Whatever... I don't care about it
that much. I won't insist on calling it 4.5 just because it seems to make some people mad and there doesn't appear to be any reason to do that.
But step back for a moment. It's all new books that replace the old books. No, you don't have to buy the new ones... you've never had to. But it's all new books that replace the old ones. The new books do some things a little bit differently. It's not a new edition, but it is clearly a revision. Hence ".5". Seems simple to me.