This really got me at the Prerelease, since my own deck was so weak I couldn't avoid splashing.
I advised a guy beside me to go G/R, but his Thornscape Master alone was too powerful not to add white to fuel the ability, and he had all three of the elves (Quirion, Nomadic, and the 2/1), plus 2 Fertile Ground and a Harrow.
I basically think it's almost not worth it to go 2-color anymore even though some Philippine players would rather have consistency over a little extra punch before Invasion.
In general, Invasion helps 3 colour a lot. More specifically in limited though, Invasion GREEN helps 3 colour a lot. SO if you get a deck with poor green, I think the chances that you will go two colour double/triple. But even in masques, less than 50% of sealed decks should really be 2 colour.
Note the other big issue is coloured mana requirement. If your main colour(s) require double or triple coloured mana for some spells, you are much more likely to have to work 2 colour or give up consistency.
I think that B/R is very playable in Invasion and probably the deck of choice for many players. You could splash another color if draft a dual ort two but I would be comfortable playing two colors.
I agree that B/R was very playable, but i always seemed to slip in a splash of green in there, since it allowed me to play with so many good cards.
I have yet to see an unplayable 2 allied colour combination in invasion, but I believe that since splashing becomes so easy , and there are several good limited gold cards, 3 colour will be incredibly prevalent. The lines have become really blurred between limiting your options and overextending your mana. In the long run, I expect B/R with a splash of blue to become very popular as blue is a great splash colour and can lend a lot to that decktype.
Side note: If you thought rochester drafts were ugly with Masques, wait til you see invasion. THere will be a lot of colour sniping and severla very aggravated top 8 drafters in the next month. Since I cant go to the qualifiers for various reasons, it should be tons of fun to read about. Let the war of words begin.
Before the Invasion Prerelease here in the Philippines, the country's top-ranked player at Worlds (#2 in Asia, too) already posted on the local mailing list that Invasion would be a draft headache!