Top N and Remaining using dynamic filter

See if this works for you. 

Create the measure for the revenue for each period:

Revenue Current Period =
CALCULATE (
    SUM ( 'Table'[Reporting Currency Amount] ),
    FILTER ( 'Table', 'Table'[Reporting Period] = "Current Period" )
)

Revenue Prior Period =
CALCULATE (
    SUM ( 'Table'[Reporting Currency Amount] ),
    FILTER ( 'Table', 'Table'[Reporting Period] = "Prior Period" )
)

Create the RANKs for each period:

RANK by Revenue for Current Period =
IF (
    ISBLANK ( [Revenue Current Period] ),
    BLANK (),
    RANKX ( ALL ( 'Table' ), [Revenue Current Period] )
)

RANK by Revenue for Prior Period =
IF (
    ISBLANK ( [Revenue Prior Period] ),
    BLANK (),
    RANKX ( ALL ( 'Table' ), [Revenue Prior Period] )
)

I have this table to use as the dynamic TopN silcer:

Now create the TopN & other measures:

Current Period TopN = 
VAR MX = MAX('TopN'[TopN])
RETURN
CALCULATE([Revenue Current Period], FILTER('Table', [RANK by Revenue for Current Period] <= MX))

Current Period Others = 
[Revenue Current Period] - [Current Period TopN]

and 

Prior Period TopN =
VAR MX =
    MAX ( 'TopN'[TopN] )
RETURN
    CALCULATE (
        [Revenue Prior Period],
        FILTER ( 'Table', [RANK by Revenue for Prior Period] <= MX )
    )

Prior Period Others = 
[Revenue Prior Period] - [Prior Period TopN]

To get

I've attached the sample PBIX