Simon Pratt said:
Are there any theories on Blackholes becoming so massive that the forces generated by the matter within them exceeds the forces compressing them and the tipping point leads to a Big Bang?
We'd have to know the configuration of the interior of a black hole to know that, which would require an understanding of quantum gravity. But my guess is probably not.
The issue is that once you have a black hole, and pressure which is added to the system to prevent further collapse just increases the gravitational attraction. According to General Relativity, there's simply no way for any stable configuration of matter to exist inside a black hole.
The only way out of this would be for quantum gravity to produce a different result. And my suspicion is that it just won't have anything analogous to the bounds for neutron or white dwarf stars, as very different physics will be involved. But we can't really know without a quantum description of the interior of a black hole.
Edit:
To argue a little bit further, the limits for neutron and white dwarf stars rely upon the Pauli exclusion principle, which is based on there being a specific number of particles. The no-hair theorems for black holes do not permit particle number as a valid property of the black hole, possibly indicating that the interior matter within the black hole cannot behave like a fermionic fluid.
Granted, the fully-quantum treatment of gravity might still turn this on its ear. It's hard to know.