When looking at the WRs one-by-one it looks concerning. There’s the youth/uncertainty to be instant contributors (Harry and Meyers), availability due to diminished health (Thomas) or off-field concerns (Gordon).
Assuming Edelman is hopefully a sure thing, that leaves 2 spots for 6 names being discussed who you hope can be a legit #2 and #3. The odds seem pretty good that 2 out of 6 in Gordon, Harry, Meyers, Dorsett, Thomas, and Harris can fill those roles when looking at it optimistically.
Did a little exercise to see how the Pats 4th WR has done in recent years, as they aren’t typically as significant in terms of production as maybe they are on teams that rely more heavily on 3-4 WR sets. When checking past seasons for the distribution of receiving yards going back 5 years it’s typically been 2-3 WRs, 1-2 TEs and 1 RB accounting for the top 5 spots. Here’s the order for those spots, plus where the 4th WR ended up.
2018: RB, WR, TE, WR, WR...WR4 6th with 290
2017: TE, WR, WR, WR, RB...WR4 8th with 194
2016: WR, TE, WR, RB, TE...WR4 7th with 243
2015: TE, WR, WR, WR, RB...WR4 7th with 269
2014: TE, WR, WR, RB, TE...WR4 7th with 82
Obviously receiving yardage distribution is just one element to the story, and not indicative of success on the field. Also this doesn’t factor in the impact of injuries and how they skew these stats (ex. Losing your top WR/TE midway through the year). I think what this does tell us though is that the loss of Gronk/a weaker TE group means that a WR3 may need to contribute more like a WR2, WR4 more like a WR3, etc.
This could of course be partially offset by continual emphasis on the running game thus less reliance on the passing game, more involvement in the passing game from RBs not named James White, and perhaps a pleasant surprise or two along the way (Ex. Having 2 WRs blow up for 1,000+ yards each).
Anyways, sorry I’m really bored and threw all this babble at the wall..