A distant observer never sees any matter actually absorbed into the event horizon of the black hole. So for a distant observer, the black hole remains massive and continues to attract more mass.
The mathematics of this is interesting. But you can get a feeling for it by thinking about what happens to light emitted by the incoming mass just as it passes the event horizon of the black hole. To the distant observer that light is motionless as space is moving across the event horizon at the speed of light. In actuality what the distant observer sees is the frequency of light from the matter decreasing as the mass moves towards the event horizon. The result is that no matter how long you wait (weight?) you never see the matter (forgive pun) crossing the event horizon.
So for the outside universe the mass of the black hole never decreases, except by Hawking radiation, which is essentially negligible for all massive black holes.
On the other hand, if you look a the math in the local corr system, we see the matter crossing the event horizon (of the distant observer) and being absorbed into the central singularity. At some point, due to tidal forces early on, or due to mass compression near or in the central singularity, the temperature of the matter rises above the Higgs temperature, the Higgs symmetry is restored, and the mass of the matter disappears.
I expect that in the heart of the singularity, the unified field is restored and symmetry is perfect. The unified field is massless, being purely bosonic. I also expect that the unified field is in 26-d. So there is a phase transition from 10-d where fermions can exist. Matter or fermions, even when massless, cannot exist in 26-d according to string theory- only bosons, or force particles of very high energy.
According to General Relativity, mass and energy are equivalent. So it may be argued that gravity is not affected in the transition from mass to energy. But since this is happening at the Planck scale or close to it in the singularity of the black hole, all bets are off. No one can even guess what is really happening until we get a theory that unifies quantum mechanics and general relativity.
Hope this answers you question. The short answer is that mass is just static energy, and that gravity comes from energy, not just mass.