1) Firstly bitcoins are not anonymous (if you want to buy them via an exchange the exchange demands personal information which it will hand out to governments.) Secondly you keep assuming that maybe when bitcoin ever becomes anonymous (how?) it might be used for a fringe purporse instead of cash. Why? Why not use cash to buy household appliances and whores. Again its much more cumbersome to use bitcoin. Also you dont explain how the business selling you household appliances will evade taxes via bitcoin.
Most people will not want to evade taxes.
2) Again if this guy is operating a small/ medium/ larger business he will need to pay taxes. Having customers is a public act; if you buy stuff with profits that are physical this is true also for the software entrepreneur. How do you know what business he is operating and if he is going to report tax?
3) Again why would anybody use bitcoin for fringe small time transaction and not cash? Yes if you buy something from him and he lives in another city. But how will you know about him? Via websites offering products? Public and therefore not anonymous for the person selling these products via the web.
Serious and competent businesses dont evade taxes. Nobody wants to risk jail time.
4) No that would assume governments loosing the money monopoly. You have not addressed my points concerning small, medium and large businesses and tax controls.
1) So you think the government will create special divisions for checking the profits people made on btc based on their exchange balance? I find that improbable. And what if someone kept btc in his wallet for years and never converted to fiat? How would you trace him? Don't forget that Ulbricht managed to prosper until he made a mistake of placing his site code on some software forum. Most of the dealers who sold on his site weren't captured. And we are talking about drug dealing and big profits. The system can't even deal with that, how will it deal with Joe sending his son money without reporting it to the higher power?
Everyone I know would prefer to avoid income tax as it is unjust. I also know a lot of people who do not report their side jobs. Look what happened in France when they increased the taxes.
2) Why would I care?
3) You really never used craigslist type sites? So you think someone will knock on your door and ask you if you've been doing gardening plumbing or whatever for John Doe because they saw him leaving you a message on some advert site? Give me a break

What about TOR network?
4)They will lose it anyway, you can't print money forever.