I need to move 2 speakers in my home theater in the basement but have run out of speaker cable. Thought I had left enough in the ceiling to accomadate any place I needed to move the speakers. So my question is do I run more cable or could I get away with splicing about a 5 foot piece to the speaker?

Electronically, splice it.

Make a connection that cannot oxidize. Two methods come to mind, solder and crimp.

Soldering seals the metals with a metal fill between them so that the connection cannot corrode. This will work.

Crimp connectors, properly applied, cause the metal to cold flow just a bit, which forms an oxygen-free connection between the wire and the splice on one end, and between the splice and the wire on the other end.

BUT --
Practically speaking, if something should go wrong with these connections in two years, will you have access to them to correct the situation? It is always a risk to drywall a splice....

I saw the ultimate in this at a store once, where the wall had been built with 2 x 6s, and Matrix Technology relay switching boards had been mounted between the studs. Then the wall was drywalled, taped, mudded, painted....and never serviced.

I did this. I crimped and then sealed with heat shrink to help prevent future corrosion.