I won’t give you the name, because I don’t know it. Based on the Russian and Soviet history, this will be someone who combines all three attributes:
- Knows how to lie low and bid his/her time. “Don’t look conspicuous, it draws fire / Try to look unimportant, they may be low on ammo.” (—Murphy’s Laws of Combat).
- Is a part of Putin’s inner circle, or someone a step or two lower on the ladder, with a noticeable performance record in the state bureaucracy
- Is personally very wealthy, or has access to an ample war chest through his family or personal friends.
This person may come to power either immediately after Putin, or as a successor after one or two transitional figures, like Dmitri Medvedev (too weak and doesn’t have his own power base).
There is also some chance of a “non-systemic” opposition leader coming to power (think Navalny). But this requires a physical removal of Putin from the Kremlin, which may happen only as a result of a dramatic split in his inner circle. Right now, I consider the chance of it considerably less than 0.1.