SISU would sell now if someone met the asking price. Just no-one's going to do that.
If we went up chances are any potential bidders would offer more, but SISU would want more as well.
However, given the level of investment needed in the Championship to be competitive, let alone go for promotion is a massive increase on L1, and without any certainty on the ground issue that'd make it doubly hard to do.
Money we'd get from Championship wouldn't be enough to think about a new stadium, plus by the time it'd be finished we'd likely have dropped back down again due to not being able to invest in the team because the money was going on the stadium. Not that I've ever believed SISU were genuinely ever considering it as a option, just a scare tactic.
Even if we were able to get back to the Ricoh, if the team struggled in the Championship crowds would quickly dwindle and if we were in St Andrews they'd be pathetic.
I think for SISU their best choice in that scenario would be to try and get out ASAP after promotion was secured as it's likely the highest point they'll be able to take us and thus when they can achieve maximum value, but then they'd have to accept they still probably won't get as much as they'd ideally want. There is of course the ongoing legal issue regarding the Ricoh but would the potential gains from that on the chance they won be worth more than the value of being a Championship club, which is not guaranteed for long? IMO it isn't. In a shrewd way it could also make them look better in terms of ownership because then all the issues with finances would pass onto the new owners and if they failed to keep the team in the Championship they'd look bad, the fans would be unhappy and there'd be a bit of historical revisionism on SISU as owners.