That chart doesn't look promising.... I'm starting to get worried.
I wouldn't say the chart is indicative of cause for concern. The true question for concern would be # of subscriptions, or total hours of play logged.
Of course HTC is not going to release that information; nor would I expect or ask them to.In the grand scheme of things, that high spike could very well be supported by a blitz of advertising by HTC. An AD blitz would likely bring in loads of two-weekers trying out the game. They are easy kills by the fistful and drive up the total kills count. They get frustrated and don't extend into a subsription (of course some do, but clearly not all). The good news in that 'assumption' is that the two-weekers don't pay for the game so HTC has not really lost any of the 'fixed player' base, even though the chart/stats make it appear that way.
Same thing goes for the total lowest rank of 6000+. I too remember a few tours where the rank showed 6000 or more. But the question would still remain, was that during the ad blitz and how many of those 'lower' ranks were non-paying two-weekers.
Anyway, my point is that I don't see the game dropping off, nor do I see HTC being negatively affected. If you re-examine Lusche's graph and take out the extreme anomalies, the average line is basically steady.