If history repeats itself, they'll be getting a Mack Coaster soon, 2019?
I know that's a common theory- that whatever one park gets, the other will get something similar. And it has happened sometimes, and I understand why some think that. But it really only plays one way, sort of, and there's been a lot more investment at Dollywood than there has been at SDC. And several things put in one park that didn't have a matching cousin at the other.
Since 2004, Dollywood has added 7 coasters (Thunderhead, Sideshow Spin- now closed, Mystery Mine, Wild Eagle, FireChaser Express, Lightning Rod, and Whistle Punk Chaser). Of those, 2- that's right, two, had matches at SDC, one sort of with Outlaw Run, and the other being the Grand Expo coaster.
Then you get the other additions in that same time period:
2005 Dollywood Renovates Country Fair with 10 new rides- matched by Grand Expo at SDC the next year
2006 Dollywood adds Timber Tower- no match
2008 Dollywood adds River Battle- matched by SDC's River Blast
2010 Dollywood opens Adventure Mountain ropes course- no match
2011 Dollywood adds Barnstormer- matched by SDC's Barn Swing
2015 Dollywood opens the DreamMore Resort (nothing close at SDC)
2017 Dollywood opens Drop Line freefall ride.- no match
The one thing that SDC has done in that time that Dollywood hasn't was replace Geyser Gulch with Fireman's landing which contains exactly 0 (zero) new rides, but all ones that have been in the park previously or recycled from other parks (especially Celebration City).
So since 2004, Dollywood has added 5 coasters, 3 major rides and a resort with no comparison at SDC. That also doesn't include the 2 new areas of the park they've added in that time as well- Thunderhead Gap/ Timber Canyon and Wilderness Pass, as well as a couple they've expanded.
There may be a compliment to this at Dollywood, but honestly I hope not. it would be nice to see them invest in SDC for a change and not have to do it at Dolly as well. SDC deserves some of the love that's been going to TN over the last few years.