You do realize that by nerfing Flash again with a "slightly longer cooldown" your not really fixing the problem right, the only way to get less people to take Flash would be to remove it.
Personally I'd like to see you get rid of Flash in order to promote the agressive value of Surge, because Surge has a summoner spell that counters it, just like Ignite does.
Surge is countered by Exhaust and Ignite is countered by Heal. The only thing that counters Flash is Flash so if you don't take Flash then your instantly trying to handicap yourself and put the game in hard mode because so many other people are going to take Flash that you won't be able to effectively escape ganks and kills you would get will escape thanks to the short range teleport.
Then there's champions like Tristana, Ezreal, Riven, Kassadin, ect. who already have the extra mobility from utility abilities in their kits which essentially allows them to double jump in order to secure a kill or become monsters at turret diving.
I personally believe that the game would be much more balanced and "risky" if Flash was gone, and it shouldn't be there because it doesn't have a counter. I am looking forward to the the allowence of Barrier but I can't really say I'm looking forward to the other"new" spells because they aren't new, your trying to make them competitive with the utility of Flash which I don't believe will happen as long as Flash remains available.
You never hear in a champion spotlight how the Surge secured a kill, or how a Clairvoyance found the enemies camping in the bush for a counter initiation, in every Champion spotlight though, you'll hear at least 3 instances of Flash saving the champions skin or securing a kill, and Phreak recommends Flash for everybody, the only time I clearly recall him not recommending Flash is in the horribly outdated Renekton spotlight.
Keep Surge, dump Flash, and make people rotate into actual tactical strategies. If there is no Flash then the difference of summoner spell selection will immediately increase expotentially.
On masteries though I am looking forward to the mentioned changes, some more versatility in the trees would be amazing and it'd be great to see what the team has come up with.