Well, those Dreadfleet models don't look like they would be quite compatible with Man O' War models. At least, the models have been so updated that they would make the non-updated models look craptacular. I also suspect that there's a difference in scale. If GW were going to release more models (expansions perhaps) to round out the fleets then that would be great. I suspect that's not going to happen though.
So if GW were to do a BFG version of this, such as an updated re-release of Space Fleet, then it probably wouldn't be all that great. I say this because if they were to pour their resources into this sort of thing then they'd probably discontinue production of BFG models. If they didn't do that then at worst this would be neutral news (ie, models incompatible with BFG or merely reproduced BFG models).
Having said all that it could possibly be a good thing for BFG. If GW don't discontinue BFG and the models are compatible (scale/style) and they're new models then this would be great, else GW suck balls. This is the algorithm of GW success. They should pay more attention to it.