There are never any guarantees, but the fact that the Survivalist series is relatively short, gives it a better chance to be completed. Still, as noted here by Outlander, it is all a matter of economics. If sales do not provide a satisfactory return on investment, GA will ultimately invest their resources in another series, or other projects, to maintain a desired rate of return.
So the best thing is to support and buy the books you like, until they complete a series or stop.
The Mack Bolan/Executioner series were what brought me to GA in the first place, and I love the GA productions and buy each when they come out, but it does appear as if not enough people have continued to support them with sales. I'm disappointed, but that's business. It looks as if the STONY MAN series is doing well enough to continue, though, and I really like that GA went back to the beginning and have recently completed STONY MAN DOCTRINE and the other early books in the series. In the mean time, I discovered the Deathlands series and others that GA produces that I've tried and now enjoy, especially some of the westerns (PREACHER and LAST GUNFIGHTER, for instance).