It wasn't major when they were adding various "Other Bitcoin Links" (Largest Transactions, Bitcoin Nodes Globe... )
So I guess it is not just about querying realtime blockchain DB
It wasn't major when they were adding "Send via email or SMS" feature
It can't be anything requiring Bitcoin-Qt sourcecode changes.
It can't be free giveaway.

"Major" announcement... hmm...

Could be Litecoin wallet and litecoin blockchain.
I am not sure those bitcoin dev team are friendly to litecoin... are they?
If this is the case, it will affect litecoin price rising. Also, some expectation for other alt coins could be made.

Fiat-Bitcoin exchange is a major, or maybe way more than a major.

I think it will be multi language support. This is beneficial only for bitcoin. Chinese language is highly likely.