I'm going to be the oddball here and vote No to the topic, but for a slightly different reason. By the end of Heavensward I finally came to the conclusion that I hate GL as a class mechanic. In the 2.0 days it was exciting because it was both new and showed you were playing your class right, but at this point it's just outright annoying to take into any content. Instead of feeling like a reward for playing correctly it feels more like a baseline you need to meet in a game where bosses love to be untouchable just long enough for you to lose it.

Ultimately though I don't see how GL4 would improve anything on MNK's gameplay. After 4 years it's incredibly stale and could use some serious revitalizing. The way MNK is played in PvP feels much better than PvE and like an actual growth. A quicker access to GL3, chakra's rewarded for completed combo's along with a damaging way of gaining them, "stances" actually having use (though this is subject to the nature of PvP) and Tornado kick getting real consistent use. An actual growth to the class would do more than just a bit more attack speed.