A pump, of course. I remember it happening with Litecoin and doge, was funny, unless you timed wrong your entry and exit points
A pump can increase the price. But it is just in short term. And the price will drop in medium term. Just like what happened in 2013-2015.
BTC can't really be compared to DOGE or LTC, an abrupt increase in the price due to the halving will be surely followed by a correction \ drop but still to a price higher than the starting one.
Ultimately, in the medium-long term, the laws of demand/offer will affect BTC price too.