October 1st isn't very far away and if a restricted free agent doesn't sign his qualifying offer by then that QO will expire. That means the player will still be restricted but will no longer have the option of accepting the QO. For the Suns that means they will still have the right to match any offer another team makes Alex Len but unless that happens Len could possibly have no contract (and no paychecks) at the beginning of the upcoming season if he doesn’t accept that qualifying offer by Oct. 1. The Suns do have the option of extending the QO up to March 1st but teams rarely do that and so far there hasn’t been even a rumor of another team being interested in extending him an offer sheet.
Len isn't the only RFA in this boat as fellow RFAs JaMychal Green (Memphis), Nikola Mirotic (Chicago), Nerlens Noel (Dallas) and Mason Plumlee (Denver) also drew no offer sheets from other NBA teams and have not yet signed their QOs. All were likely expecting generous offers like those teams have thrown at other free agents since the salary cap ballooned but with this year's cap falling below expectations and many teams having already overspent on free agents last year, that well has dried up.
Just last year former Houston Rockets player Donatas Motiejunas did not sign his QO (which Houston decided not extend past Oct. 1). This is an excerpt from a Hoops Rumors article that sums up what happened to him:
"A year ago, it was December before Donatas Motiejunas finally found an offer sheet, but that lucrative four-year deal with the Nets fell through after Houston matched it — the Rockets and Motiejunas couldn’t agree on incentive details, the forward skipped his physical, and the two sides eventually parted ways. Motiejunas, who later signed for the minimum and is now out of the NBA, could act as a cautionary tale this fall for RFAs who don’t yet have a deal when training camps begin."
If Len doesn't accept the QO, the Suns aren't required to make him an additional contract offer but if they do they aren't required to offer him any more than a veteran's minimum one-year contract. That would cost Len about $3 million in salary if he accepted that and he would still wind up in the same situation at the end of the season that he would have been in if he had signed the QO, an unrestricted free agent looking once again for a new contract. The unrestricted free agent market hasn’t been much better this year either for role players - which is basically what Len is at this point - and many have been signing contracts with teams in Europe, China or elsewhere.
Len could also choose to sign to play for a team overseas this season instead of accepting the QO but the Suns would continue to own his rights if he decided to return to the NBA. According to the NBA’s Collective Bargaining Agreement (CBA), the Suns could also either relinquish their right of first refusal (making Len an unrestricted free agent) or submit a new qualifying offer the following year which would once again make Len a restricted free agent and the Suns would have the right to match any contract offer he would get from any other NBA team. It's doubtful that Len could get an overseas contract that would be anywhere near the amount of his QO (approximately $4.2 million) and also doubtful that the Suns would relinquish their right of first refusal and just let Len walk.
Alex Len's options are limited and in six weeks they could grow even smaller. Unless some other team comes out of the blue to make him an unexpected contract offer between now and then, his best bet would be to sign the Suns' qualifying offer on September 30, stick with the Suns for one more season and take his chances as an unrestricted free agent next year.