Some altcoins price risen but are not noticeable really. We all notice the greens when BTC also spiked to its new ATH. If there is a reason for you to sell while you are already in profit, why not. It may never go up again, you said it yourself this altcoin bull run may not be a big as it was before.
The ones reason why some of us actually believe the atlcoin season today might be bigger is because of the ETFs filed by difference institutions. Can;t say whose right or wrong but just don't get your hopes too high.