From what I understand, Rick is going to make "the system" much easier to create importers for other products, so i'd imagine that we'd definitely be able to knock out the majors (Fusion, vB, IPB, SMF, phpBB).
I'd imagine that Rick would update the importers for v8 for the ubb to be able to bypass ubb7 for those coming from ubb6's, but I'll wait in anticipation with you
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I'd like to include that I'd still like to see a UBB.t7 to UBB.t7 (or even UBB.t8 to UBB.t8) importer; I've got a couple of forums installs that I'd love to combine, and that's just not possible right now...