During the opening keynote of the GPU Technology Conference, Jen-Hsun Huang unvailled the codenames and the roadmap for the next 2 generation of NVIDIA GPU architectures !

So we now publicly know that Johannes Kepler and James Clerk Maxwell are the two next scientists that will succeed to Enrico Fermi !

Sources : 

It's interesting to note that communicating so early about unreleased architectures is a major change in NVIDIA marketing strategy, that was used to keep the architecture names and the roadmap secret.
NVIDIA started to communicate publicly about it's architecture names during the release of the first Fermi chip, the GF100, but the previous architecture codenames were never publicly communicated even if the information was available online.

For instance, the name of the Tesla architecture that was the one used in the G80/G9x/GT2xx was unveiled half-publicly through a very good paper from NVIDIA describing the architecture: NVIDIA Tesla: A Unified Graphics and Computing Architecture

All previous NVIDIA architecture names were also discovered a long time ago by the crazy hardcore reverse engineering people working on the NOUVEAU project:

So for the complete family of NVIDIA scientists (according to the NOUVEAU project):
  • Celsius : nv10 
  • Kelvin : nv20 
  • Rankine : nv30
  • Curie : nv40
  • Tesla : nv50/G80/G9x/GT2xx
  • Fermi : GF100/GF10x
  • Kepler (2011)
  • Maxwell (~2013)