That's what I hope(d) as well! I'll buy the VG-C70AM battery grip probably in December, and it'd be great to be able to mount in on the A900 as well (would make the upgrade less expensive). However, in a previous thread (don't know which one), we already came to the conclusion it wouldn't fit. The A900 is wider and the battery compartment and tripod mount, which are both needed to attach the grip, are further apart on the A900.
That's not official though, just some good thoughts of other CL members. It seems more than likely that the A900 will be bigger than the A700. However, on the pictures, they look quite similar...
I searched for some pictures of both grips, so we can compare them:
As you can see clearly in the image, the grips are indeed different
! The Alpha logo in printed on the A700's grip, like it was on the DSLR-A100. The A900's grip has got a similar logo as the DSLR-A700 body.
Also, the arrows of the joystick on the A900's grip are white, instead of black (on the A700's grip). Last difference is the place where you'd rest your thumb, on the A900's grip, there's clear edge, which is not visible on the VG-C70AM.
So not very good news for all A700 + grip users would like to upgrade to the A900 some time (including me
- Bjorn -