DX won't be updated to a new version again. It came out July last year with 2.1 and was soon updated to 2.2. That's two updates they'll already have given it. Ice cream sandwich (not keeping up with googleio xplorer?) won't even be released until Q4. So assume Novemberish, although GB was released the first week of December with the same quarter target. By the time moto screws around with it, it gets through VWZ, the DX will be two years old (or almost there). Way past the "attempt to keep updates rolling for 18 months for all new phones" initiative they announced yesterday.
The D2G on the otherhand... should be just within that window...hopefully/maybe.