We shall see. Remember that when rejoining the EU are going to try and get the best deal possible for themselves. I think you'll find that public sentiment can turn very quickly under such circumstances.
You are also assuming no problems in the EU (such as an Italian debt crisis) meaning that rejoining has real negative downsides as well.
The final process to rejoin the EU would at a minimum look like this:
- Referendum on rejoining EU - Negotiations with EU on what exactly that would mean - Some sort of deliberative process to determine if rejoining under these conditions is acceptable.
This will not happen for another decade at a minimum. And a lot can happen in that time. And if part of that agreement is the UK loses control of its borders again then I would bet money on no agreement being reached.
Does the EU want the UK back?
Remember, the debtors aren't being bailed out, the creditors are. Otherwise creditors would import products from these countries and be made whole very easily if it was about bailing out the debtors.
In practice it doesn’t look this will even be an issue, since Brexit is already producing such bad results and losing popular support as demographic changes wipe out its base of support.