Oh I don't think OTN or WAN-PHY have any large deployment future, the cheapest option is 'good enough' and whatever value you could extract from OTN or WAN-PHY, will be difficult to capitalise, people usually don't even capitalise the capabilities they already pay for in the cheaper technologies.
Of course WAN-PHY is dead post 10GE, a big reason for it to exist was very old optical systems which simply could not regenerate ethernet framing, not any features or functional benefits.