Not so. Each day this goes on more and more evidence is being piled on - or else the investigation would conclude and they'd go with what they already have. The more evidence that Mueller gathers the harder it will be for Trump to remove him.
Not only that, but each day this continues further damages Trump with the Republicans, be it the politicians or the more non-partisan Republican voters. This weakens his power to act autocratically, and also makes it difficult to fire Mueller.
Legally Trump cannot personally remove special counsel. Not without first removing the laws that prohibit him from doing so, which as I understand he can, but that is a slippery slope. Only the AG has authority to do so and only with reason, since Session's recusal himself now that power rests solely with the deputy AG. So this was already made less than improbable the moment the AG recused himself.
If this investigation is still ongoing after September that would be indicative of some major crimes. There will be a feeding frenzy of lower-level Trump staffers offering testimony in return for immunity.
I love the presumption of guilt. This is still America.
If they uncover any major crimes my guess is the investigation will turn to prosecution sooner than later. Personally, I'd be surprised if the investigation
didn't carry over into next year, as the language that formed the special counsel was so vague as to put few tangible limits on what they could investigate.
"authority to investigate and prosecute federal crimes committed in the course of, and with intent to interfere with, the special counsel's investigation, such as perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses."
Emphasis is mine. But "in the course of.." basically gives the counsel cart blanch to investigate
anything Trump or his team is doing
right now that may seem suspicious on a Federal level, not to mention anything they can remotely connect to the Russians or the election. So in theory the longer the investigation stays open, the more they have to look into. Its an unusually wide purview, typically special counsel investigations are a bit more focused.