If I understand this post there are two issue (in RoR) which conspire to create the problem:
1) session cookies can be stolen
2) session cookies remain valid after logout.
The attack does not apply to web2py because 2) does not apply.
Web2py since 2.7.x reissues session cookies when users sign in. That means that an attacker who steals a session cookie after the legitimate user signs out, cannot use it sign in.
Of course 1) still stands and session cookies can be stolen. Which means that an attacker who steals a session cookie can sign in while the legitimate user is also signed in. This can be preventing by forcing ssh.
I think we are fine.
Massimo