It is possible that some farmers would abuse it, but that would be expensive and unnecessary, since the target weed would die with a regular dosage.

Abuse of glyphosate spraying is also counter-productive. Low volume sprayings are generally more effective.

And by the way, glyphosate-resistant does not mean glyphosate-impervious. Non-targets can still be harmed.

The risk of over-usage of glyphosate is re-enforcing naturally occurring resistance in target weeds. Glyphosate should always be used at intervals, with different herbicides filling in the gaps.