Here is the thing. Everybody is expecting "buy the rumor, sell the news" because of what happened with BSV and BCH after the halvings. So since everybody is expecting a dump? Most likely it won't happen.
i wouldn't say "everyone", maybe a very small portion of people think that way but the majority either don't know what altcoins do or don't care. and keep in mind that these two are not the first shitcoins that didn't get a pump for their halvings and instead were dumped big time as miners left. much bigger altcoins like LTC expereinced the same thing. at this point people are aware that altcoin halving is equal to miners leaving and them dumping but bitcoin halving always means more miners coming and price shooting up to a new ATH.