While this may be disheartening for people who don't PVP since they don't like it, aren't good at it etc. I also understand that the extreme limit on the items given out is another part that makes people give up before trying.
I looked at Season 1 results, the average matches played for 1-10 was about 560 for single queue and 230 for party queue. About 790 matches. The results for 21-30 were about 320 for single queue and 120 for party queue, about 440 matches total. However, there were people in season 1 and 2 with 500+ matches that did not make the top 30. It is not impossible to reach the top 10 and stay there it will take some effort.
On the flip side...
To the people who are good at PVP and The Feast, be careful how much you gloat. There will probably be a large influx of people who are not good at your favorite game mode and can quite frankly, ruin YOUR ability to proceed as well. Yes, you could build up a lead and sit on it, but if people really want these rewards, you may have to return and defend your spot on the leaderboard and lose it. I wouldn't gloat too much.
In the end, I think there will be tons of salt all over from both groups, PVPers and non PVPers, especially for solo queue. Be careful how much salt you rub into the wounds of others, you may get some in yours too.