The Path of Exile team has recently started a thread about game mechanics where players can ask questions of the gameplay programmers. From time to time, a round up of all those questions is posted that answers a boatload of them. In the latest posting on the PoE site, tons are answered on topics as wide-ranging as whether or not there is a technical limit to DPS, if Arctic Armor Reduce can reflect fire damage, strongbox queries, whether or not there's a taunt cooldown period and many more.
Is there a technical limit to DPS?
There is a technical limit to the visible DPS on a skill popup, due to that being stored in an integer variable. There is a technical limit on the amount of damage a given hit can deal (same dealio), but to my knowledge not a technical limit on the number of times you could hit a target in a second, so I do not believe there's a technical limit on actual DPS dealt to a specific enemy.
There is definitely a mechanical limit to DPS, because there are limits on how high the values of stats you can obtain from passives/gear/etc. There is some theoretical "best DPS" build that could exist with perfect gear, that would have more DPS than any other actually possible build. This limit is significantly below where any technical limitation would occur on actual damage.
Read the entire post on the Path of Exile site.