I agree HC, I see in the future most shops will be sold off by the landlords and reverted back to residential rather than A1, or A2. A lot of the high street stores are under 'internal only' repairing leases now and the repair costs to LL's for roofing and damp issues is extremely high, so they will start to sell off.
In the meantime, the quick turnarounds will be A3-5 - cafes and fast food as planning is easier to obtain and the income easier, especially now that the cafe culture is growing and people are spending more time in restaurants to catch up with friends and family. However, leasing a flat above such fast food sites is less appealing to new tenants due to the noise and opening hours, so the Landlords's income will drop if they have more than one floor to rent out with less interest. Eventually they will cut their losses and move onto residential only properties and the high street's will become part of councils re-development schemes but in a different light - less emphasis on trade, and more on creating nice areas to live.