First of all PyQt is approximately 37k/12k lines of code (python/c++). So buying it would be a waste of money since a couple of programmers can write a replacements in few weeks (especially if you own Qt).

The move not to change PyQt to LGPL is short sighted of riverbank. They could have made increased income with bookdeals for mobile devices.
Nokia is clearly pushing Qt to all of their mobile platforms. With future releases of Qt the python bindings of PySide are likely to change and introduce incompatibilities with PyQt making it obsolete at which point riverbank probably will release a LGPL version when it's too late. Microsoft would call that EEE.

By the way, using Boost.Python is a good choice and should make porting easier.