I have games with TH6, TH7, TH8, and TH9. Using bases with the TH inside the walls NOW is a decent enough preview of what is to come. Most attacks are from the same TH level; and they actually tend to lose the attack. However, the kill my heroes and clan castle troops, so the next attack has a much higher probability of succeeding, especially if it is one TH above. Every once in a while, I get attacked by a player two TH levels above, but that's actually fairly infrequent.
And, yes, we will be able to attack through a shield, but that assumes you know when you were attacked and have the time to do so. An overnight attack will exhaust most of that shield, of course.
Most current attack strategies should work the same post-update as they do today (that was one of my points) although holding on to trophies will be a bit harder due to the lack of snipeable THs. The big problem here is the short PBT and being unable to save much across raiding sessions.
This update will weed out a lot of players; the casual player and the not-very-good will quickly jettison themselves. Why? Because it will simply be too difficult to get and retain resources to build up the base. By the time you hit TH7, maybe TH8, the game play will drop to the point of taking 6-12 months minimum to upgrade a base (well...without rushing). After this update, you will also no longer be able to play on just what you mine/collect/drill either; in fact, for TH7 and up, resource collectors will simply be a means of slowing down your opponent and increasing the likelihood of getting a shield.
it's possible there are other changes that will improve gameplay, but I am skeptical that will be the case. In the meantime, I am one raiding maniac right now while I still have the six hour PBT. Of course, on deployment day, I will be sniping like a mad man too; for the first month or so, there will be tons of loot available to TH snipers.

