Is there currently a shift from -nce word endings to -ncy word endings?

As noteed by Jason: An interesting way to investigate changes over time is provided by Google Ngram.

LINK

in which they use the word "resiliency", rather than "resilience".

The -cy suffix had several functions depending upon the root word. The examples in question are perhaps clearer than most in their original meanings (Quotes from OED):

"resiliency" -> a tendency towards resilience

†1. Tendency to rebound or recoil. [...] Obsolete.

1651 tr. J. A. Comenius Nat. Philos. Reformed x. 189 Why those things that are to be seen must of necessity be enlightned? because sight is the resiliencie [L. resilientia] of the light from the object to the eye.

resilience - the attribute of being resilient.

I. Literal applications.

†1. The action or an act of rebounding or springing back; rebound, recoil. Obsolete.

1626 F. Bacon Sylua Syluarum §245 Whether there be any such Resilience in Eccho's

Despite the obsolescence, the "-cy" may reflect a tendency to be cautious about absolute claims, as the "-cy" version appears to have more of the abstract about it.