PNP was pretty fast till October or so, some applicants were receiving PPR in like 70-80 days also. Then it slowed down, only CIC knows why. Maybe because of the increased number of files in other streams specially FSWO, in my opinion as far as I have studied recent trends, they have slowed down CEC also in May, so i think they are trying to balance out the load, as FSWO has maximum population in here.
I have a theory (it is totally speculation and maybe totally wrong) but i think-
It takes the longest to verify FSWO files and is easier for CEC (due to canadian records) and PNP (due to prior verification by the province), hence they are assigning UCI numbers after 100-120 days to PNP applicants, maybe they think that they can easily clear the backlog for PNPs and hence giving priority to FSWO instead. The FSWO backlog is being accumulated more and more everyday owing to maximum number of candidates being issued ITAs are FSWO. As of May and June so far CIC has clearly given preferance to FSWO in assigning of UCI and medical pass.
Though May CEC got medicals and UCI late then FSWO but many of them have already got PPRs as the BGC is easy for them, i guess, and also CIC has mentioned that CEC is priority stream for them as they want to people with canadian experience to easily settle because those people are already in the system.
So now left is PNP, hence this stream due to less number of applicants then FSWO is given the least priority these days. This can be easily changed also, CIC is very very unpredictable.
As for your rejection question, for PNP as per current trends when medicals are passing after 100 days, i don' think you can be sure of anything till then. After IP2 you can say that chances of rejection decrease.
Your only option is to wait here my friend.