Phinis Gestor of the College of Winterhold mentions 4 missing apprentices, he even lectures about "Any information as to the whereabouts of the previous groups of Apprentices would be greatly appreciated." But if you find all 4 dead apprentices and bring their respective named items back to Phinis, there's no option to tell him of their fate.
Birna of Birna's Oddments in Winterhold will sell you a Coral Dragon Claw and says that if you find anything with the claw, let her know. Even if you find something using the claw (Yngol's Helm in Yngol Barrow), she doesn't have the option to inform her.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
The above examples are just a few of the instances where I feel the game seems unfinished. Things that get started, or mentioned in passing, but never really materialize.
Hopefully, Bethesda will tie up these loose ends in a patch or coming DLC (highly unlikely). But in case they don't (I think extremely likely), perhaps we could come up with ideas to tie up these loose ends.
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
Please post ideas and feedback on how these things could progress
What I've come up with so far:
A Beneficial Partnership: Help Ysolda buy the Bannered Mare and give Hulda the retirement (nonviolent!) she yearned for.
Requirements:
1) Bring a Mammoth Tusk to Ysolda (part of Vanilla Skyrim)
2) Bring 10 samples of Sleeping Tree Sap to Ysolda (part of Vanilla Skyrim, now with a requirement)
3) Be Thane of Whiterun (to show that Ysolda can trust you, since you're a person of stature within Whiterun)
4) Have at least 15,000 in gold (buying an inn costs money!) to give to Ysolda.
Once you reached the above requirements, Ysolda will have a speech option to ask her about buying the Bannered Mare. She will say that the two of you can be partners: she will run the inn and you can be the investor (hence the 15K gold). She then ask you to go to the Bannered Mare and make a deal with Hulda. Once you meet with Hulda, she will agreed to sell you & Ysolda the inn at varying amounts (15K gold if your Speech is pathetic, or as low as 10K if your Speech is really high). She also mentions that she will continue to stay at the inn as a guest and will look after the inn if Ysolda travels as part of the deal, since she enjoys the atmosphere and banter.
Benefits: You get a daily stipend from Ysolda in gold. Ysolda will be behind the counter in the Bannered Mare and able to sell you inn goods at discount prices.
There are various issues to work out if your character marries Ysolda AND she become the new owner, but I think they're minor and could be solved.
The Tales of Four Apprentices: Inform Phinis Gestor the fate of the four missing apprentices.
Once you have locate the four missing apprentices and bring back their named items, Phinis Gestor will give you better prices on his wares, as well as give you 1 free level in conjuration. He will also stop his Hall of Elements lecture about missing apprentices.
Bad Deal Gone Good: Bring the unique item found with the Coral Dragon Claw to Birna.
Requirements:
1) Purchase the Coral Dragon Claw from Birna
2) Explore Yngol Barrow and obtain Yngol's Helm.
You have the option to keep the helm, or bring it back to Birna. If you bring it back to her, she will give you leveled gold, as well as better prices.
Firir's Fate: Inform Eydis (at Old Hroldan Inn) of her husband's fate in Chillwind's Depths.
If you bring Firir's note to Eydis, she will thank you and gives a leveled enchanted weapon, saying it was her husband's. If you just inform her without giving the note, she will just thank you and gives some gold.
Most of these will probably be unvoiced since I doubt we could get the original voice actors to collaborate

Anyways, I'm probably missing a few other instances. So feel free to suggest, comment, and give feedback.