Is it the role of ICT, e.g. booking platforms, recommendation platforms; is it a change in players on the tourism market place, is it the transition towards sustainable or health tourism etc.?
"Most influential" depends on how you define influence and whom the influence will affect. However, a rough guide to answer your question can be to check the most cited articles of tourism journals. For example the currently most cited articles in Tourism Management are:
Role of social media in online travel information search by Zheng Xiang | Ulrike Gretzel
Tried and tested: The impact of online hotel reviews on consumer consideration by Ivar E. Vermeulen | Daphne Seegers
A review of innovation research in tourism by Anne Mette Hjalager
I think you are spot on. The interface between ICT and tourism has attracted a lot of attention recently. In addition to that, the interdisciplinary nature of tourism activity, along with developments in emerging (tourist) markets (such as a lot of Asian countries) has received considerable attention. A cursory examination on the latest volumes in the Annals of Tourism Research will probably attest to this phenomenon.
Complexity theory applications that demonstrate that X relates to Y positively, negatively, and not at all in both surveys and experiments and responds to the need to see specific cases in output in data analysis. Such analyses are occurring now in tourism and hospitality research. Very exciting development. For example, "Applying complexity theory to deepen service dominant logic: Configural analysis of customer experience-and-outcome assessments of professional services for personal transformations." Pei-LingWu ⁎,a, Shih-Shuo Yeh b,1, Tzung-Cheng (.T.C.). Huan c,⁎⁎, Arch G.Woodside,Journal of Business Research 67 (2014) 1647–1670. Also see Critical Tests of Multiple Theories of Cultures’ Consequences: Comparing the
Usefulness of Models by Hofstede, Inglehart and Baker, Schwartz, Steenkamp, as well as GDP and Distance for Explaining Overseas Tourism Behavior, Shih-Yun Hsu1, Arch G. Woodside2, and Roger Marshall, Journal of Travel Research 52(6) 679–704.