I think at best it will have moderate success, and at worst it will be a disaster bigger than Vista. There's no way it can be the "most successful ever", for 3 reasons:
1) Windows 7 has that title covered, because people waited for something like it for 10 years, and were very frustrated with both XP and Vista. It also came at a time when there was still no competition in sight for Microsoft. There was a real, painful need for Windows 7. There is no such thing for Windows 8. Plus it arrives at a time when people just got Windows 7 and they are happy with it.
2) Windows 8 does a dramatic change over previous Windows versions, which means most users are much less likely to be interested in it because most users don't like change, and Windows 8 would have to follow the technology product life cycle all over again (innovators -> early adopters -> early majority, etc.). So it has to actually convince people to use Windows 8 over anything else out there, including Windows 7.
3) People are less likely now to be interested in a Windows machine. You have Macs which are getting increasingly more popular (at least in US). You have iPads and Android devices. You even have Ubuntu and Linux Mint which are starting to leak a bit into the mainstream. The point is, the competition landscape is a lot less friendly to Microsoft right now than it was for previous versions over the past 17 years.
1) Windows 7 has that title covered, because people waited for something like it for 10 years, and were very frustrated with both XP and Vista. It also came at a time when there was still no competition in sight for Microsoft. There was a real, painful need for Windows 7. There is no such thing for Windows 8. Plus it arrives at a time when people just got Windows 7 and they are happy with it.
2) Windows 8 does a dramatic change over previous Windows versions, which means most users are much less likely to be interested in it because most users don't like change, and Windows 8 would have to follow the technology product life cycle all over again (innovators -> early adopters -> early majority, etc.). So it has to actually convince people to use Windows 8 over anything else out there, including Windows 7.
3) People are less likely now to be interested in a Windows machine. You have Macs which are getting increasingly more popular (at least in US). You have iPads and Android devices. You even have Ubuntu and Linux Mint which are starting to leak a bit into the mainstream. The point is, the competition landscape is a lot less friendly to Microsoft right now than it was for previous versions over the past 17 years.