I'm surprised nobody has posted a thread on this yet, but probably new iPads have been spotted in iOS 11.3 references and in Eurasian certification documents recently. That suggests a new iPad release in a month or two.
French: https://consomac.fr/news-8126-la-keynote-de-mars-2018-se-confirme.html
Translated to English: https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https://consomac.fr/news-8126-la-keynote-de-mars-2018-se-confirme.html&edit-text=&act=url
The New iPad (2017) always struck me as a temporary stop gap, so the possibility that it only would be a year before the new model came out in 2018 wouldn't surprise me.
French: https://consomac.fr/news-8126-la-keynote-de-mars-2018-se-confirme.html
Translated to English: https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https://consomac.fr/news-8126-la-keynote-de-mars-2018-se-confirme.html&edit-text=&act=url
The New iPad (2017) always struck me as a temporary stop gap, so the possibility that it only would be a year before the new model came out in 2018 wouldn't surprise me.