We dont know…it depends on how much people want these things…Avast! still performs damn well with 0-day malware and regular tests from mrg tests…check my links in previous posts here on this topic…please check the links pondus posted.
Avast! has over 165+ million users…more than any other antivirus…explains enough on how good avast is and why so many people use avast! 
Also,dont you think there is something fishy with AV-C?? always promoting the top industries…I mean those results must change…Why is it constant only with top industries being promoted…Not to mention everyday the nature and amount of malware coming out changes…and I test AV’s regularly and everyday 1 is a loser and another winner…same goes with BD,KIS etc…I can show you a test in which avast 7 defeated BD and miles by miles…
BD left in ransomware in my tests…that avast blocked with signatures…KIS left in Zaccess…again which avast was neatly blocking it away.
Believe me …that test is flawed…always promoting Top industries…and btw trend wasnt even there on top so far…and immediately they come to top impossibe because trend AV is still useless and only Web blocking is good.
Believe the tests that show variations like MRG,shadowserver etc…I dont believe on AV-C
Detecting unknown threats…Hmm only heuristics can do that…and believe me that…No AV detects a lot if unknown threats…because heuristics or any other things cannot detect even 1% of the unknown malware Unless its a HIPS.
Also,do you remember flame…the unknown threat that went undetected for years…who caught it?? no one not even KIS.BD ;D
said enough…avast sandbox is damn effective right now with detecting a lot of nasty things atleast from my tests. 
Just be happy with what you have and dont watch tests and dont care about them…use it if it works for you and be careless about the others.
With more than 10000000 of malware coming out…dont expect any AV to score 99 to 90% … its not possible…its just over-exaggeration.
check the Shadowserver tests…toppers…even they show the same 90% crap…when its not possible…you can test against 1000000 of samples and still the test will not be accurate because of the influx of malware coming out everyday… :o
Google and research the threats coming out everyday: http://www.zdnet.com/blog/bott/the-malware-numbers-game-how-many-viruses-are-out-there/4783
So,Prevention: preventing a system from being infected from the malware that’s out there right now…the latest that come out today…does your AV detect them??? for your answer avast does keep its game on top from my tests.