The short answer? Not really.
The amount of friends you have left that are still playing Miitomo
Answering random questions each day can become very tedious even though the subject of these questions is usually different. Seeing friend's answers can be interesting, but only if they continue to use the app and answer the questions asked of them. I've already noticed a sharp decline in some of my friends participation in Miitomo based on the lack of new answers for me to read and comment on. What started as a wildly popular app that myself and others were curious about, has now become something that only the most die-hard Miitomo fans can care enough to open every day and devote time to.
It also doesn't help that the amount of reward given to players is far less than the amount of effort they'll have to put in to get these rewards. Coins that are available to purchase new clothing items from the shop are very limited unless you want to spend real life cash to get more. The interesting clothing items don't come cheap either. Some single pieces will cost close to 2,000 coins, while special costumes or full outfits will cost around 4,000 - 7,000 coins! That's an absurd amount, considering how few coins are awarded to the player. It may take weeks or maybe even months to accumulate such a fortune, by which point you probably won't be playing Miitomo anymore anyway.
I'll have enough to get that Cowboy outfit when Autumn starts!
Today was the first day I can honestly say that I didn't care about clicking the Miitomo icon on my phone's home screen. The daily bonuses that kept me coming back for more just aren't as enticing as they used to be and my friends' presence in the app is all but nonexistent. I'm sorry Nintendo, but I don't think the popularity of Miitomo will last very long, even if you have reached 10 million users worldwide.
Nothing I can say or do will keep my friends playing Miitomo in the long run
That's not to say that Nintendo hasn't tried to keep us playing. They even recently began a Splatoon x Miitomo crossover that introduced new Splatoon themed shirts, shorts and other gear from the Wii U game that fans would love to get their hands on. In addition to that they also have new Miitomo Drop machines every few days with new clothing pieces.
When it all comes down to it, this gamer feels that Miitomo is on its way out, although it was a good first attempt at a mobile app for the Big N. Let's hope the Animal Crossing and Fire Emblem mobile games will turn out better!!