firstly segwit guarantee's nothing.
when activated. nothing changes.
users have to wait for yet another implementation release that offers the actual p2wpkh/p2wsh key utility
AT VERY BEST .. IF 100% of users used p2wpkh/p2wsh keys instead of legacy(old) keys, expect maximum of about 4500tx instead of ~2500

but here is the thing
spammers, scammers and bloaters wont use p2wpkh/p2wsh keys. so dont expect 4500tx a block
even moral people take months/years to upgrade their implementations. so even after it activates dont expect noticable rises anytime soon

and lastly. the mempools is very often full of more than 4500tx unconfirmed at most times. so many transactions are still going to be waiting even in the utopian statistic of 100% dream utility.

segwit is just an empty gesture kicking the stone down the road