This year there seems to be a real chance that Youmu will reach first place.
I already speculated about that being a possibility last year "if Youmu somehow managed to replenish her popularity among the general Touhou fandom" and that seems to be exactly what has happened over the past year.
>Youmu became playable in WBaWC and reaffirmed her role as playable character of the main series
>many promotions capitalizing on Youmu's surge in popularity and status as the third playable character
>strongest and most popular character in Lost Word, which has already surpassed 1 million downloads in Japan
>multiple significant manga appearances that became popular topics on the Japanese internet for days
These factors also led to a massive increase of fan art on Pixiv in May, the most fan art in a single month since 2013 and it didn't even have a Youmu day.
That being said, first place isn't going to be easy. Koishi might be an even bigger threat than Reimu and Marisa.