Is such a final י after a consonant often (or perhaps always) pronounced as a diphthong?
I misread your comment (did you edit it?). It might imply an /i/ sound or an /ay/ or /ey/ diphthong. Both are common.
Depends on the niqud of the consonant.
I didn't edit it. I know it all depends on the niqud but I've already noticed that there are some patterns that tell you how this sound is likely to be pronounced in a certain context. So I was wondering if י is often pronounced as /aj/ at the end of a word. I've seen some words for which it is true and I don't remember any other pronounciation (at the end) so I thought maybe that is the case.
It is a common structure with words that are a singular-first-person plural possesive, eg. my books would be ספרַי, my doors might be דלתותַי etc. So you can expect to see it around. It's not a rule per se, but it does show up often.
אולַי has a similar structure, by chance.
adding the letter "ש" before a word is like saying "that...", so the only way "שאולי" might be used substitution for "אולי" is if the sentence said "that maybe", for example "I think that maybe you should go"-"אני חושבת שאולי כדאי שתלך"
Scrolling through some of the comments here on duolingo (can't recall where exactly, though). I know that this word might also be some sort of variation of the well-known Hebrew name, but in the sentence that caught my attention it was definitely used as a substitue for אולי. Could've been just a mistyped word as well. Anyway, I was curious about it and since I couldn't find any relevant information on the Internet, I simply decided to ask it here.