Wave 5 is IMO going to reinforce the current metagame. It will bring a little more diversity in turret ships and give the imperials a Falcon equivalent, but it's really just going to be a case of "which of your 3 turret ships do you want to spend 50+ points on". The only way I can see it making much of an impact is if adding even more turrets finally kills off the ACD phantom and indirectly opens up the metagame again.
This is guaranteed to happen to an extent. The uncertainty will be in how big of an impact it will be. The counter to HLC Dash will be even more specific than existing Phantom counters: you will want PS10+ (or 9+ with initiative) post-dial reveal movement. PS10+ Engine Upgrade, in particular, is going to be a very good counter to Dash.
I am really against 4 dice 360 Dash. That doesn't sound fun. Sorry. Just not fun. Not casual. Not flying.
Have you actually played against HLC Dash, or are you just assuming that the sky is falling? Remember that there isn't all that much difference between HLC and Falcon + gunner + predator/marksmanship, and getting the HLC turret means giving up gunner. The HLC hits you hard with one attack and punishes low-agility ships like b-wings and decimators, the Falcon gets the same end result by making you spend all of your defensive tokens and then hitting you again against unmodified dice.
3 dice with Gunner is more reliable, especially against high agility targets. But 4 dice HLC, especially with TL+F, is going to do more overall average damage, especially against lower agility targets.
PS 8 if you want to get a lock on Dash. That's the important part. If dash is moving at PS 9 he wont have both a boost and barrel roll and will be considerably less dangerous.