If 80% miners signalled activation of BIP91,there will be no split.Is it correct as currently 76% have signalled it and with 11 days remaining, 4% more could join.
If that happens,there will be no split?
That is incorrect. There can still be one or more splits. However these splits may not be persistent. Those miners who are not following the BIP 91 rules will find their block orphaned. Since there may be 20% or more (because of variance, BIP 91 could activate without 80%) of miners who are not following the BIP 91 rules, they could end up mining a small fork of the chain briefly before the rest of the miners mine a chain longer than theirs and causes a reorg. Furthermore, with the prevalence of spy mining, miners who are enforcing BIP 91 may accidentally end up extending a non-BIP 91 chain because they are mining before validating.
The same issue would happen if BIP 148 had majority hash rate support, but because it does not, BIP 148 would likely result in a persistent two chain split.
This is all becoming very confusing now. Please allow me to divert the topic a little. What is the current status of Segwit2x now and will it be successful in activating Segwit?
You are asking us to predict the future; we can't do that. BIP 91 currently has almost 80% hash rate support. With some luck and variance, it could activate soon. Whether it actually does waits to be seen. We cannot predict the future.
Furthermore, even if BIP 91 does activate, miners may not be actually enforcing it so it may not even activate segwit.
If the answer is yes, then what will happen to BIP148?
If BIP 91 activates, then it will require all blocks to signal for segwit. This is the same as what BIP 148 requires after August 1st, so, assuming that there are no chain splits because of BIP 91, BIP 148 nodes will follow the same chain, and after August 1st, both will be enforcing the same rules.