Discuss why you think they will/won't below. Personally, I'm rooting for more exotic trades, such as selling/buying cocoa beans, and/or other various goods. Seeing mostly the same offerings from villagers gets boring over time.
Trades (certainly in the later versions) have been adjusted more based on "game-balance" than "logic" (eg. the removal of the raw beef trade in 1.8 & raw mutton added in the same version has never had a trade in vanilla).
The shepherd (each of which has 18 [!] trades, if one counts each wool color as seperate), is a similar example: all the colors appear to have been added so that all the wool colors would be available – even to players who had not secured a supply of all the dyes. ]
Given the number of people complaining about how "over-powered" villager trading is in its current iteration, the chances that Ms/Mj would expand the options seems slim…[ …with the posible exception of newly added villager types. (Bedrock seems to be doing a number of things with villager trading, further diverging from standard minecraft: vigilance will be needed.)]
This is unfortunate as some new trades might fit quite well:
Ink sacs [particularly given the greater rarity of squid in 1.13+], seem perfectly logical purchases for Librarians and Cartographers (as do feathers, but adding that would create a backlash )
Feathers [but see supra] and Flint for Fletchers [although the Stonemason (currently only in Bedrock) might be more logical as both a buyer and seller of flint.]
Rotten Flesh being added to Fisherman might be justified as bait. [That Clerics also but this item does not seem prohibitory, given the number of professions buying coal....]
Beets for Farmers was mentioned [although – given the otherwise limited uses – there might also be backlash here…]
Shears have always struck me as more appropriate to the Toolsmith than the Shepherd, but some form of sheep feed would make sense: Haybales seem better than wheat to me (both as more logical and to differentiate the trade from the Wheat trade of the Farmers).
Some of the more exotic Dyes (the dyes themselfs, not any of the dyestocks) could also be appropiate for Shepherds. (Grey, Orange, Lime, Cyan and Purple seem least likely to occasion outcry if added – with interaction with the Cleric lapis trade needing careful attention for the latter two.)
Armor pieces to complete the sets seem logical for both Armorers and Leatherworkers ("gamebalance" being the likeliest suspect for the current gaps).
Of the trades mentioned above; only Ink sacs, Flint (purchases), Haybales, and the mentioned dyes seem likely not to precipitate significant resistance [Note that none of these (with the exception of haybales) will feed a composter.*1] (The old adage of "If it ain't broke, don't mess with it" [oft misquoted as ", dont fix it" – but an unbroken system is in no need of fixing in the first place] will certainly be seen as applying to any change for the sake of change, or attempts to coerce playstyle…)
*1 As discussed in another thread, wheat is significantly better than haybales as a composter input; so much so that composting haybales seems unlikely ever to occur.
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WARNING: I have an extemely "grindy" playstyle; YMMV — if this doesn't seem fun to you, mine what you can from it & bin the rest.