I'm not going to detail what the fork is all about, there are enough better informed articles out there anyone can look up, like this.. https://bitcoinmagazine.com/articles/bitcoin-beginners-guide-surviving-bgold-and-segwit2x-forks/

Essentially though the question is, what happens to Bitcoin, B2X and the alts after the fork?

The newly SegwitX2 forked Bitcoin is called 'B2X'.

Bitcoin IS the brand, it IS the news and to the masses, it IS cryptocurrency. So whatever happens to Bitcoin does have an effect on the whole crypto market, like it or not.

I see 3 Scenarios and here they are in a nutshell with some knock on effects!

Scenario 1 - Bitcoin remains top dog and rises in price.

B2X takes some market share but is essentially another crypto (yes it has faster transaction times and more efficient with lower fees BUT so do many other cryptos which are NOT Bitcoin(The brand)). B2X still will be able to use the brand but there can only be one real Bitcoin.
In this scenario, I see Alt coins becoming stronger, this scenario sheds light on other tech and why not use another fast tech like Litecoin/Dash or something much cheaper like Pivx?
Alts could take a hit in the run up like with BTG fork but should bounce back right after and resume as we have seen, steady rises for strong tech and steady losses for yesterday's coins. Remember there are over 1100 crypto currencies and more tokens and new releases every day.

Scenario 2 - B2X essentially becomes the NEW Bitcoin (Bitcoin 2.0?)

It works a lot better, the banks like it, the institutional investors prefer it, etc, and money pours into it (raising the price and overall market cap), the old Bitcoin could become known as the slow, dinosaur type tech that no-one really wants anymore and price starts to drop, think of older versions of any tech, Windows/Apple IPhones/Programming languages - Unfortunately it is very common. Alts also have light shed on them in this scenario because the King has been dethroned, new and better tech is being considered so top 10/20 alts get a lot of money pouring in.

Scenario 3 - New King is crowned - Not Bitcoin!

Nobody liked the new fork, its a step too far, the brand has been weakened. Bitcoin is still Bitcoin but now only known for a store of value and as mentioned in scenario 2 looked at as older tech. Other versions of Bitcoin are not as trusted now although B2X is a success of sorts, but finds competition with strong Alts offering better solutions. Mass adoption looks at other tech, Litecoin/DASH/Monero/Ethereum could get the top spot. This could take a month or two to play out as FUD eventually starts to clear.

Conclusion and what it means for Alts

In this run up there is a lot of FUD about Bitcoin and also FOMO on B2X. After all if you are not in BTC you wont receive the equivalent in B2X. In order to get the new forked coin people may flee the alts causing prices to drop in the run up. Once it is clear what the outcome is post fork. Strong alts will do well IMO.

I hope Strong alts do not go down in the run up, possibly people are already positioning themselves for the Scenario 3? I say possibly because it is a collective opinion which drives the market, something known as market sentiment. Has the Bitcoin brand been weakened? Is it someones diabolical plan to weaken Bitcoin, are we overlooking the bankers power and banker friendly coins like Ripple? Or is this all about Bitcoin 2.0?

Post fork, without any Black Swan event that could crush the crypto market I think Alts will have room to move up, there will be more exposure and a growing market cap.

Good luck in positioning your holdings.