should i worry about my btc?
There is a huge difference.
BitcoinXT fork is 75% of the Bitcoin community agreeing to allow for phased in block size increases.
Altcoins are copies of Bitcoin changed significantly and started from scratch so that n00bs can think that they are early adopters and they're going to get rich some day.
And the blocksize code is just a code enhancement to the existing Bitcoin protocol. If forking actually caused an alt coin then Bitcoin is already an alt of the pre-2013 fork version of Bitcoin.
Bitcoin code is upgraded all the time.
Correct, the average user will not even notice the change should it occur.
I would enjoy some additional selling into my orders, though. However once no sellers exist at these levels and volume/volatility begin to dry up, the path of least resistance is up.
Last time I checked, Bitcoin is still functioning as intended.