Tor nodes build encrypted TLS sessions between neighbors to multiplex circuits of users. Multiplexing helps to anonymize users (?).
With an increasing number of middle relays multiplexing becomes rare (because Guard nodes... and Exit nodes are some "predefined" set).
Can it happen that with an increasing number of relays (often middle relays) timing attacks become much stronger? (maybe I could use netflow, etc. ...) Extrem case: each circuit has it's own middle relay.