It really all depends which browser will be released with the final version of Fremantle -- and, then, which browser you choose to install/use on your own. We don't know yet what features will be available in the stock browser. Fennec has tab-like functionality; installing Easy Debian Iceweasel will give you a full tabbed interface. I currently use Webkit, but it doesn't do tabs. (Does Tear use tabs?)

As Bundyo said, someone from the community would probably have to figure this out for MicroB under Diablo.

Tim