4L60E going?

Hi, I'm new to AF and have a trans question about my 96 Sierra Z71 4X4 with 350 Vortech. The truck just turned over 200,000 miles and about 6 months ago the trans started acting up. When it's up to normal temp at highway speed, sometimes the engine will gain about 2-300 RPM like it loses the last gear or converter lockup. After around 5 miles it comes back in and doesn't do it again. No SES light or anything. Is this a sign the trans is going to fail soon?

A couple of things can cause this, first it should be scanned with a trans function scanner as this happens, second a skewed tps can cause this also.