Last try to make you understand the basics of bitcoin mining.

Consider 5 mining pools, each with 20% of the hash rate and with "difficulty in equilibrium" which means that ON AVERAGE there's 1 block every 10 minutes in all, and each pool wins a block every 50 minutes on average (1/5 of the blocks).

Up to here, I hope you are with me, OK ?

Now, consider that the first 4 pools switch off, but the difficulty level remains unchanged (it will not change for the next 2000 blocks).

Well, the fifth pool will still make his blocks every 50 minutes, and that's it.

So:

1) the fifth pool won't see much of a difference in his rate of winning blocks (namely about 1 every 50 minutes on average, with exponential probability distribution)

2) the total chain now being made by only this pool, the whole chain only wins 1 block every 50 minutes on average.

This is a very elementary notion in bitcoin mining.  If you don't agree, you've seriously misunderstood something.  Go ask elsewhere if you don't believe me.  Until this point is cleared up, there's no point in discussing other aspects of the bitcoin system.