I'm sorry, this is a really tough situation.
I hope that your wife has had the decency not to start an affair with her friend but you should prepare yourself that she might have done. I don't say that to hurt you - but there is a reason she has ended your marriage now, and whilst that might be because she knows she wants to it further with her friend, it might also be because she already has.
As for not selling the house for 2 years? A mistake, I think.
Firstly, you need to be practical. Will the equity in the house fund two other houses or are one or both of you looking at mortgages? Because you must be in your 50s I'd guess - even 60s. So 2 additional years could make a big difference to how easily you can get a mortgage.
If there's any chance she hasn't cheated and might realise what she's giving up, that's more likely to happen with a For Sale sign outside the house than without.
You're not going to lose your son. He's 23, he could fly the nest at any time. And even though it's heartbreaking to not live with him now when you could be, that relationship was always going to have to make a transition soon. You won't lose him.
It's probably unrealistic to stay in the same house for two years. You happy watching her date? Happy that in a year you might want to date and a woman might say to you "no, messy - I'm not dating a man still living with his wife".
I would say to her - you don't want to end it, and would she go to counselling? If it's a no, tell her you'll take legal advice, suggest she does the same - and start to take action.
Good luck 