Being a long term bitcoin holder i am little scared.some people are even saying bitcoin might fall to zero after August 1st.is that even a possibility?should i sell my bitcoins to cashout profits and wait it out? or should i keep holding?
In my opinion, you should closely follow the news.
There are three possible scenarios:
1)
Segwit2x succeeds. Then you have nothing to fear and you can keep your Bitcoins where you want (in your wallet or on an exchange), although some here don't like that solution. You can track the adoption on
http://coin.dance/blocks. However, be warned that the transition is a bit complicated - what now is showing up as "Segwit2x support" is only an informal "signalling" without consequences. It gets interesting around July 21 when signalling for BIP91 begins. If BIP91 gets rapidly to over 80%, then Segwit2x is basically through.
2)
Segwit2x fails, but BIP148 gets more than 50% of the hashrate. This may be a possible outcome if Craig Wright decides to block Segwit. In this case, most probably we will have two chains: the Segwit chain and the legacy chain, and maybe the often-cited "Chinacoin" if Bitmain releases a big-block chain. However, if BIP148 has majority support, I think you are safe on that chain because it most probably will have most of support from Core and the users and price should recover fast after some turbulences. Still, I would recommend you to transfer your coins to a real wallet before August 1, so you can sell also your "Chinacoins" if you want once both chains are cleanly separated.
3)
Segwit2x fails, and BIP148 fails, too. This scenario is the most bearish of all, because we will have uncertainty which chain is the longest, and very probably the Bitmain fork will take place and even get some support.
In this case, I would chose fiat. How to know if that will happen? Simply look if on
http://coin.dance/blocks Segwit2x support goes under 70% and at the same time on
http://www.uasf.co/ less than 20-25% are signalling for BIP148 (actually, it's about 10%).