I think that IOS tablets will stay the second best behind Android but not behind Windows because Windows, at this current point in time, do not have a big enough application store to compete with the Apple App store. However, Android hand held devices have already overtaken Apple products because of their wide range of quick and efficient devices are knowingly better than Apple.
I do not think Windows-driven tablets will overtake Apple's iPad tablets in the market of mobile devices. Apple appears to dominate the technology market and always has innovative ideas. I personally prefer Apple to Windows because of the sophistication, style and quality of their products. I do not see the same in Windows, and it appears that most people out there buying tech products agree also.
I like some of Windows' tablets but I do not see them overtaking Apple's iPad. The iPad is the superior device and is a much better product. The iPad may cost more but it is worth every penny. It also has a better reputation than any of the Windows tablets.
I do not think Windows tablet will be better than Apple's Ipad tablets. I think Windows took too long to debut a tablet to compete with Apple. Apple's Ipad is the most popular and will continue to be regardless of what Windows put out to try and top the Apple's Ipad.
Apple makes excellent but expensive products, and they have a design that appeals to many but not to all. The Windows and Android tablet markets will grow, and that provides healthy competition, but it seems unlikely that Windows will overtake Apple outright, especially since Android is also a player in the market.