So for once the rumours - or part of them - seem to be true.
MadonnaTribe has heard and can report that the Madonna team is indeed working on plans to hit the road again this Summer.

It won't be a proper new tour, but rather an extension of last year's show. It is currently planned to last two months - July and August - and it should mainly visit cities where the 2008 tour hasn't stopped. Also. as of now, this is shaped as a European tour only.

It is probably too early to say which countries will be included. Marseille in France made the headlines today with yet to be confirmed reports of Madonna performing at the Velodrome in mid-July.
The other stops that have been mentioned the most by the rumour mill so far have been Milan, Italy, where Madonna is rumoured to play San Siro's Meazza Stadium, and a short residency at Greenwhich's O2 Arena in London, England.

There is certainly a lot more in the making so it will be better to wait until an official announcement turns rumours into facts, but the most discussed topic in the Madonna online community in this beginning of 2009 seems indeed to be true: Madonna will extend the Sticky & Sweet tour with a revamped show next Summer.