Serviced hub the other day and noticed some corrosion on one side of the cups. Have repacked and tightened it all back up. Is this likely to cause any problems or do I need a new wheel in the near future?
Its not corrosion its wear caused by age, ill adjusted cones, a bent axle or insufficient lubrication. The worst that can happen is that the cup collapses sending your wheel sideways into the frame causing you to grind to a halt in the middle of a busy intersection. Its unlikely though. I would ride the hell out of it until it annoys you enough to want to replace it.
Keep with it - the hub will run rough, but you'll get away with it for a fair bit. Just look after it.
Now if it was your super duper steed, then new hub/wheel/wheelset...
My commuter has this issue on the rear hub, but I've got away with it by using some spare ball bearings and a spare (used) cone - it runs slightly rough, but it will do until the rim wears out - the front isn't too great either... but a regular re-grease will help.
Had this been on my 'best bike' then a new wheelset it might be !