You can still only have 5 concurrent batch process running at one time. Salesforce (with the FlexQueue) have introduced a new status
Holding, such that you can have (per org) a maximum of 100 jobs in
Holding, and a maximum of 5 either
Preparing (but not Holding) or
From the docs
Holding Batch Jobs in the Apex Flex Queue
With Apex Flex Queue, you can submit up to 100 batch jobs without getting an error.
The outcome of Database.executeBatch is as follows.
- The batch job is placed in the Apex flex queue, and its status is set
- If the Apex flex queue has the maximum number of 100
jobs, Database.executeBatch throws a LimitException and doesn’t add
the job to the queue.
When system resources become available, the system picks up the next
job from the top of the Apex flex queue and moves it to the batch job
queue. The system can process up to five queued or active jobs
simultaneously for each organization. The status of these moved jobs
changes from Holding to Queued. Queued jobs get executed when the
system is ready to process new jobs. You can monitor queued jobs in
the Apex Jobs page.
So, if you did flood the queue with multiple requests, you'd get a Limits exception, so its still worth checking the number of jobs prior to doing that.