If Ubisoft send AMD copies of the game, and write it in a way that AMD can work quickly with them to create a CrossFire profile for the game come March. Then yes. But sadly no one know what Ubisoft or AMD are upto or working on, or what communication they are having if any.
The term "Multi GPU Support" is quite subjective. I wouldn't take this as anything other than "compatible with different GPUs" unless they state CrossFire or SLI. Like the word "help" in toothpaste adverts, you will "help" flatten the earth by stomping, but wont mean it will really make a difference.
Its likely AMD will have an update with a profile around that time, but otherwise you should look at these claims as just marketing jibber jabber. Unless Ubisoft or AMD officially confirm it.