Nope, there would be absolutely no advantage in doing that. KTVU on channel 2 is an extremely strong station -- one of the top Fox stations in the country, as well as a very successful competitor in the Bay Area. In contrast, KRON on channel 4 is by far the weakest of the five legacy VHF stations (yes, I know that most of them aren't actually transmitting on VHF frequencies anymore, but most viewers don't know the physical channel, just the channel the stations ID as).
So going from channel 2 to channel 4 could only be a negative, even if they transferred the KTVU identity and programming over to channel 4. There's just no benefit in doing this.