I agree with Scrubber. I think the new something "uniquely Rare" will be something new and unique, hence a new IP.
Anyone who's been following Rare closely these past few years is probably aware of the many Rare IPs that are either passed on to new developers (Killer Instinct, Conker's Big Reunion, and Yooka-Laylee [as Banjo-Kazooie's spiritual successor]) or were canned long ago (BanjoX, Conker's Other Bad Fur Day, Perfect Dark Core, and Kameo 2).
If it is an old IP, I think it will be the long-awaited Battletoads (little market competition, plus Phil Spencer's t-shirt, anyone?). Otherwise, I'm sure that "uniquely Rare" refers to the spirit rather than an IP.
My ultimate hope is that "uniquely Rare" indicates that they are finally allowed the creative freedom and control to create as their cerebra please rather than being told what to do from the higher ups.
Even though I would love for it to be a a Perfect Dark stealth game (I believe the legendary Ken Lobb said something to that effect not too long ago), I suspect they will introduce a new IP to introduce to fans all over again.