Nothing happening to Hampden in near future. It got approved for ties at the Euro 2020 finals so has to be in current designs until then I guess.
I grew up with new Hampden. The only games I went to as a teenager were internationals. I now go to grounds all over the UK. Yeah, The feel of the place is diluted by the track and the depth of the stands. There are certainly loads of places that feel more fierce and electric for fans. But for me that's why hampden has memories, it was family friendly for great days out with dad. It's not a bad atmosphere, it's just a different one.
Could be worse. Look at England the other night. Qualify unbeaten with a game to spare and the place has all the energy of a morgue. If Scotland had done that at Hampden not a single soul would be complaining about the experience.