That's the million $ question, isn't it? Aldi has set the precedent for a new wave of MVNOs, the question is whether T-Mobile and Vodafone see it as a feasible option in addition to their mainstream networks. I'm inclined to believe that if and when Lidl enters the market (wouldn't put it past them, it's more a question of when) that they could very well go with T-Mobile. I can't imagine Aldi wanting Lidl to use E-Plus as well. T-Mobile stands to fall behind if Vodafone continues to see the amount of subscriber growth they saw in the last year.

http://de.wikipedia.org/wiki/T-Mobile#Kund..._in_Deutschland (29.52 million as of 12/31/2005)

http://de.wikipedia.org/wiki/Vodafone (29.17 million as 12/31/2005)

They will do something to stay ahead of Vodafone. The newer onslaught of debitel will also influence T-Mobile's next step.