If the future python support is the main issue, than I'd say you're worrying without any need. Support for python 2.x won't simply go away in two years, other maintainers will take over if it comes to that. If nothing else, Red Hat has taken on a serious commitment to support python 2.x for a long long time:
- RHEL 5 ships with python 2.4.3 and will be supported until Q1 2020
- RHEL 6 ships with python 2.6.6 and will be supported until Q4 2023
- RHEL 7 will ship with python 2.7.x and will be supported for 13 years after its release (so until 2027, if it ships next year)
I would ask myself:
- does python 3.x bring any advantages that you absolutely
must use?
- how much of your future python 2.x code would a) be supported for longer than 2027 and b) require a large rewrite to switch to 3.x (can you keep your code both 2.x/3.x compatible, or reasonably close)?
A strong "yes" to the first question wold make me choose another framework. A possibility of the large rewrite would make me consider another framework.
That being said, we use RHEL for our customers and web2py is our framework of choice for our current and future projects. YMMW.
Hope this helps a bit.
Regards