Do you think Windows 8 will gain a substantial market share against Android and iOS?

Yes.
I think it is inevitable.
Almost Every laptop that you see in the market today runs on Windows8.
On the other hand Intel x86 based chips are approaching the power profiles of ARM.
Windows8 PCs, tablets and convertibles are going to get slimmer, lighter and even more portable.
However I would like to add that it would be substantial.
There is no guarantee that windows would be the market leader.
It would be a serious contender if you want to build apps for it.
I guess Microsoft caught the trend towards tablets early enough to come up with Windows8 that is optimised for touch.

No, MIcrosoft is soo late.

People were asing the same question when windows phone were introduced in the market.

But it dint capture even1% of market

I think Microsoft is very very late in this market.
And Windows8 is still in there early phase and still it is not as good as it is expected.
How iOS and Android captured the market? Just because of hardware.
No.
They captured the market with the help of device abilities and good quality applications to utilize that hardware.
Until Microsoft does not ease the application development process for developers they will not be able to again market share.
We have experience in iOS and Android app development and recently we developed application for Windows Surface and Window Phone, it was painful experience :)