There's no incentive for Qualcomm to catch up. The flagship handset manufacturers have nowhere else to go and really only competing with each other.

Faster chips also mean more expensive chips, which would erode their price competitiveness against the iPhone especially since they don't have the volumes of the iPhone. In particular A series chips have huge and higher spec caches compared to the Qualcomm chips, which take a lot of die space, which is the prime factor in chip costs.

Finally, for Qualcomm to bring out a super-premium A series killer they would have to know, for a fact, that all the Android manufacturers would adopt it. If they didn't the per-unit costs would make them prohibitively expensive. They just don't have the guaranteed volumes. If enough manufacturers passed, the project would be a financial disaster. It's just too risky.

Check out Samsung who had 290 people designing custom ARM cores... that were no better than stock ARM cores. I suspect there's some cultural or organizational reason why Qualcomm or Samsung could spend infinite money and still end up worse.

Why should they? The high end Android market is minuscule. It’s all a race to the bottom.