See, I don't want the high street to die because I actually quite like the experience of being in a city, whether I buy anything or not. I wish things were cheaper on the high street so I could buy them there without feeling like a shmuck. My usual shopping trips now seem to consist of an £8 rail fare, £6 on lunch and then maybe a book from Waterstones (which I would be wary of getting dented in the post) and a second-hand game from CEX. I'll then come home and order things I saw in HMV and Game for at least a third less online. Ten years ago I'd have come home with a bag of CDs and DVDs from any combination of HMV, Virgin and Music Zone, a game (probably from Game) and a book or two from Waterstones or Borders. I miss all these chains which have fallen by the wayside and would love nothing more than for our high streets to be full of diversity and competition again.
If the high street does indeed die a terrible death then I think anyone who owns property in these areas will be in for a shock. If it gets to the stage where we no longer have identifiable town centres with a heavy retail presence, then town centre property values (both commercial and residential) are going to plummet.
Only for specific markets, things like food shops and clothes shops will still litter the high street and odd trinket shops that i'm not entirely sure how they are still alive now will no doubt survive harder times than huge companies. So in one regard the high street will stay more or less the same, the demand is there and the internet isn't a full replacement for clothes stores yet so i don't see high streets disappearing anytime in the next 10 years.
However stores like Game will have to adapt to survive, as they have lost their foot in the market as being dedicated games stores that you can get pre-orders from they will have to compete against stores such as CEX who are 100% pre-owned sales. However the 1Up that CEX has is that it deals in all sorts of tech (sat navs, palmtops, laptops, pc's, dvds, cd's) not just games and bluray/HD's.
As for my typical town habits when i worked in luton i would do to greggs to get food, then CEX next door to check out prices of games and dvd's, walked round to HMV and compared prices - made mental notes of dvd's or films i might like then went next door to GAME, checked over the prices against CEX and HMV in my mind then walked down to the Gamestation to compare prices further usually bought from CEX because of the best prices or only bought from GAME if i knew i had cash on my reward card and it was on offer.
So far i can only see CEX competing against the online market, with free delivery its already securing a good position against Ebay and Amazon's marketplaces. The other main difference with GAME and CEX is that with CEX you get a years free cover for if the unit breaks, buying a preowned console from GAME i'm lead to believe that you have to pay for cover.