A formidable Dem candidate hasn't had any buzz to this point, especially since every news outlet is basically TrumpTV sucking all of the coverage from anything else...If a Dem candidate doesn't emerge by February or March of 2019 i believe it will be a wrap
my outlook is similar to yours in that i think trump is the front runner in 2020... there are a few developments that could lead to trump losing reelection, but not many...
one, he could work against the dem house in 2019/2020..... most presidents have to moderate their positions when the opposition takes control of either the house or senate... trump seems intent on sticking to his guns... that might not work out for him...
two, trump could get primaried or get a serious third party challenger on the right.... trump would easily win the primary battle and get way more votes than a third party candidate, but these actions could split enough of the vote to cause trump to lose the general... remember he only won by 100K in three states... it's not like it would take that much vote splitting....
three, trump could continue to be highly unpopular and the dems could run a likeable candidate... that might give the dems the edge to win...
edit: four, the economy could crash.... i forgot that one, mainly because i hope trump can be unseated without the economy going south...
it is possible for trump to be defeated, but it is not a guarantee.... i want dems to be deliberate not cocky.... the cockiness dems displayed in 2016 is a loser... not everyone thinks trump is doing a bad job... in fact, millions think he is doing an excellent job....