I am needing to increase the size of a pattern. It gives number of stitches for S-36" (M-39" L-43") I need extra large. Would XL be 48". the pattern is for a Long Sleeve Bolero.

That is a good question! It appears that 46 would give the next size up from large, following a sequence of numbers from the pattern sizes you listed.

Does the pattern tell you how long this part of the garment should be for each size? You could use a proportion to get a more exacting fit.