XP support was getting extended again and again, but finally that extended support will also end in 2014. I'm not so sure that Windows 7 Home support would end the following year in 2015. Not sure when the extended support is supposed to end, I think that's the 2020 date you mentioned. Usually Microsoft has a rule on life support end, that it's 24 month after the last service pack, and we've only seen one for Windows 7.
http://support.microsoft.com/lifecycle/search/default.aspx?sort=PN&alpha=windows+7&Filter=FilterNO
I think it's going to happen. Why? Microsoft does NOT want another XP. XP is a nightmare for Microsoft in the fact they have been basically forced to support it past when they would have liked due to various things (large companies demanding it, netbooks) It's actually the netbooks that caused Windows XP Home support to be extended. Microsoft at the time had no viable option for netbooks and didn't like that Linux was running away with the market. Microsoft makes money off of selling OSes, not so much money is made off of being forced to support an OS.
Windows XP professional support was never extended. The only reason it's longer than any other OS's support was because it took Microsoft longer than 3 years to get Vista out the door, and Windows life support is based on N+1 (mainstream) and N+2 (extended), so XP got to enjoy a long life support cycle.
Which is exactly what MS wants to see NEVER happen again

Is it so that Windown 7 Home Premium will not even have Extended Support?
Windows XP Home is the only home copy to get extended life support. As I mentioned above, that's because of the netbook market, otherwise life support for XP Home would have ended in 2009.
Also to note: April of next year will be the first major non-business NT OS to reach end of support (Vista Home, which still has 10% of the market). Microsoft has no plans on extending it.