If you believe some anonymous poster on a forum, Rockstar is planning multiple expansions for Grand Theft Auto Online through 2020. According to SoftSecrets, a GTA Forum user who has been correct on a bulk of things he's reported since 2013, says this is what is in store for the game...

Major Updates to come before announcement of Map expansion!
In no particular order

Biker DLC:
(Bikes, clothes, free roam missions)
*purchase clubhouse to activate biker free roam missions

Law and order DLC
(Police free roam and vehicles)
*Purchase police vehicles to activate free roam police missions

The Luxury Living DLC
(Mansions & Pets) 
*Purchase Mansion to *purchase exotic pets (Mansion grounds only) 

The Blaine County and Paleto DLC
(Animals in free roam) 
Animals online syncing workaround via VIP mission type activation

*Purchase hunting license and equipment to activate hunting objectives
*Purchase New warehouses and properties

North Yankton and Liberty City (Online Map expansion)
$£ Paid DLC 1 2017 sept
*Not Yet Complete

San Fierro and Las ventures
(Online Map expansion) 
$£ Paid DLC 2 2018 oct
*Not Yet Complete

Vice City.... Not until GTA VI, some time around 2020 At the VERY earliest!

San Fierro and Las Ventures were built alongside Los santos way back in the early development stages of GTAV, Scrapped on PS3/Xbox for obvious reasons!! 
After more then 3 years of re building for PS4/XBO/PC, 
Both are still being worked on with a release target of October 2018! 

Single player DLC has been replaced with Online Map expansion model! 
Mainly due to the unforeseen success of micro transactions and GTA online in general! 

Liberty City will be released September 2017.. 
The DLC will included

A Open ticket (for city slickers) to Liberty City! 

A Open ticket (for Snow Blowers) to North Yankton!

EXCLUSIVE VIP Membership (for High rollers) which grants Exclusive access to THE CASINO in Los Santos! 

Pre Order Bonus of 1 million GTA Casino chips for pre order!! 

Micro transactions can NOT buy GTA CASINO CHIPS! 

Liberty City, North Yankton and the Los Santos Casino scheduled together to keep player migration relatively balanced!! 

Liberty City will enable you to trade on the stock market, once a Office has been *Purchased! Similar to the current crate set up! 

Both DLC's will be priced equivalent to a full game!!

I've posted on this forum twice! 
(Not including this post)
one was BEFORE the release of GTAV back in 2013 (Check back and have a careful read, compare it to what we have today) and one post was yesterday (2016) 

Most if not everything mentioned in that 2013 post has been implemented or reworked into the current GTA Online we have today, from the old mission set up format, to individual heist roles, to the current free mode events!

With the Next four Updates to come, GTA Online will have utilised most if not all the work that went into GTAV such as animals, police vehicles, Stock Market, Blaine County etc.. 
Can't say much more, there on to me..... Speculating can get you in to a lot trouble.. lol

Keep Speculating and Keep up the great work GTA FORUM! 
You guys Rock!! *

The general consensus says that while SoftSecrets wasn't correct on all things, he managed to get a bulk of information on GTA V before the game was released. I tend to be leery about guys like this, as it more often than not seems like their posts are a collaboration of data mined leaks and telling people what they want to hear. North Yankton, for example, has been teased since shortly after the game's launch when someone uploaded a video of them playing in it outside of the tutorial...

Liberty City is also another popular rumor that we reported on after a portfolio of a supposed Rockstar employee exposed screenshots of the city under the new game engine.

Of course, if Rockstar was planning paid expansion DLC to the game, it wouldn't be surprising. GTA Online has been raking in money for Rockstar since it's launch 3 years ago, and I would imagine they're going to want to try and transfer the service over to whenever Grand Theft Auto 6 happens as opposed to starting all over again from scratch. 

Ultimately the thing that has me hung up is the paid DLC. Rockstar has done paid expansions before, but three years after the game? It's practically unheard of on console, but so is maintaining a strong online community for a non-FPS shooting game. 

I'm still airing on the side of "probably not" but I'm not entirely convinced this guy is wrong. Where do you stand?