Yeah, your TV will run fine with a set top box for freeview or similar..but Sky is digital anyway..unless your still using analogue Sky...very rare...
So you wont have any problems viewing TV.
Although I wonder if you were also refering to HD TV, well just in case you were....HD Programming wont be universal for years and years and years yet/...HD TV is expensive and most channels have not even started showing programmes in HD yet...and the ones that have have two channels..one for HD and one for standard viewing...just in case you wanted to know..so dont worry about changing your TV just yet