No, TATV was always meant to be the Season Four finale. If they'd somehow managed a Season Five, TATV still would have happened, they just would have done something to get around Trip's death.
Remember that they never actually showed his body. If they'd gotten the renewal notice in time, they could have rewritten some dialogue to make his status even more ambiguous before revealing he was alive in the Season Five premiere.
As he's going into the fixing chamber Phlox and Archer exchange an odd look, it always seemed to me that it indicated the plan was now in motion. The plan being whatever reason they are faking his death.