Well, I guess I went to press on the Nintendo Direct just a touch too soon -- as soon as I posted it and checked my e-mail, Capcom released a bunch more info about Mega Man Legacy Collection -- and not just on the Nintendo 3DS version! Note that the following all applies to North America only, as Europe is not getting a physical release.
Like the Nintendo 3DS release, both Xbox One and PlayStation 4 will be seeing their physical releases on February 23rd, 2016. These will be available at a price of $29.99 each, save for the Collector's Edition pictured at right -- that one, which includes the gold Mega Man amiibo figure and six Mega Man postcards -- will go for $49.99.
The regular editions for Nintendo 3DS, PlayStation 4, and Xbox One are alike in that they each include the full game, four Mega Man stickers, and a sample compilation soundtrack featuring 18 songs from the first six Mega Man games. Where they differ in content is that the Nintendo 3DS version features two Mega Man themes for your Nintendo 3DS (likely the same ones as seen in the Japanese version), whereas the HD twins will instead come with a "Robot Master cheat sheet."
Finally, here are some screens for the Nintendo 3DS version of the game and pack shots of all three, plus a better look at the gold Mega Man amiibo figure: