Bit stuck in the UK here (sorry to the OP who wanted German stuff particularly), but I do use "expect vectors" occasionally. I use it when I'm going to give a straight in or baseleg, usually for Gatwick, which will result in a significant shortcut and I want to let the pilot know that I'm going to expect him on the ground in 60 miles as opposed to 100 odd!
There's nothing wrong with "continue present heading", but I might not actually want to put the aircraft on a heading initially, or I might not be allowed to if it's not in my airspace, and there may be other reasons. Personally I know from experience regading the Gatwick inbounds through TANET, that if I let the aircraft follow the routing and turn at TANET for DET, that usually makes a pretty good heading for the straight in intercept, so I very often say "expect vectors for a straight in approach runway 26L giving you xx miles to touchdown" and then I'll put the aircraft on a heading at the appropriate time.
Cheers,
Notherner
"Keep smiling - it makes people wonder what you're up to..."